It is frequently necessary in apparatuses with a stationary component and a component movable relative thereto to transfer electric power and information or data, e.g. present in the form of digital electric signals, from the stationary component to the movable component and vice versa. In the case of circular knitting machines it is for example known (EP 0 431 674 A1) to select selector magnets for the knitting needles mounted on a rotary needle cylinder on the one band in accordance with a pattern, with the aid of information which is transferred without contact from a stationary component to the needle cylinder, while on the other hand the electric power needed for operating the selector magnets is transferred with the aid of slip rings.
In addition it can be necessary, especially with complex, largely automatically operated circular knitting machines, to transfer data from a stationary control unit to a component coupled to a rotary needle cylinder and rotatable together with this, e.g. a take down and winding up device, in order for example to establish preselected take down tensions. In such cases it is frequently also desired to transfer measurement data, which is generated by sensors, processors or the like located on the rotatable part, to the stationary control unit, where this measurement data can serve for example to monitor machine states or be used as actual values in regulating devices. Devices are already known (EP 1 085 712 A2) for such bidirectional data transfer, which operate through an inductive and contact-free coupling between a stationary component and a rotatable component. The transfer of electric power has however to be effected in the usual way with the aid of slip rings.
Apparatuses of the kind initially specified are further known (DE 44 12 958 A1), which comprise means for inductive, contact-free transfer both of electric power and of electric information. To transmit data between a transmitter module and a receiver module the one module is provided with an electrical line terminated reflection-free at the end, while the respective other module is formed as a sensor inductively coupled to the line. On the other hand the transfer of power is effected by means of a coupling loop connected to a power source, separate from the said line and coupled to a load to be supplied through a transformer.
Finally apparatuses of the kind initially specified are known (DE 196 49 682 A1) which also do have a line terminated reflection-free, in which however the power and information transfer is possible over this one line. The transfer of data is here effected at comparatively high frequencies from about 10 MHz, compared with frequencies of up to 100 kHz for the power transfer. A common transmission line is thus in fact present in use of such an apparatus. However two separate systems are also needed for the transfer of power and information.
The first-mentioned apparatuses require slip rings for the transfer of power, or trailed cables, as is known in flat bed knitting machines for example. Neither of these is always desirable on account of the resulting constructional limitations and the unavoidable wear. The latter cited apparatuses on the other hand do have the advantage of contact-free transfer of power and information but also involve a constructional outlay which is not insubstantial, which hinders their use in circular and flat bed knitting machines for reasons of cost. The same applies for other textile machines, especially circular braiding machines with rotatable rotors.